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Recorded on 14 November 2026, unchanged since
Entry #820 of UpFork’s ledger · A lesson's version: A mount window that moves mid-move mounts items mid-flick: move it when the motion settles, mid-move only near its edge Open it
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- Recorded
- 14 Nov 2026, 09:05 UTC
- Written by
- ramin-valadana_9d470b566acab5f65bdc
- Signed with
- k1 · Ed25519
- Entry hash
- 7099b89d24dda404e489c6b1f2b50dec9f3b97e287d935fb446b702b3b482b45
- Before it
- 90accac453a6d7dda84ea4d697b3e2b59c850155a143402c3f8d07182aedb576
- Record hash
- ca47a398a66cbe92628b2006fc22d59f41c55a611ff14a8380ea6613fa1d99f2
- Signature
- vu8CwEjcYDjLvh/m8NCcawvIfpLozVFgm4ChJHPdFPW5bppFXk3ZGnL/YD2qV7z+B0n8lDqz8dF7jXnqlivNCw==
What it proves
That this exact text was published on UpFork through this account at this time, about this version of this product, and hasn’t changed since: changing a letter, or taking an entry out, breaks every hash after it.
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Record format 2 (signed since the change on 2026-10-30): the author is named by account number alone; the handle beside it is read from the account.
{
"ai": {
"apps": [
"Claude"
],
"models": [
"Claude Opus 5.5"
]
},
"appliesTo": "react-native-reanimated@>=4.5 <5, react-native-worklets@>=0.10 <0.11",
"article": "a-garment-rail-in-react-native-where-each-piece-turns-on-its-hook-perspectiv",
"articleRevision": 1,
"assumed": "keeping the window centred on the front all the time was the cheapest way to have the right pieces mounted.",
"author": {
"account": "a_9d470b566acab5f65bdc"
},
"check": "flick across a rail of 40: no frame over 50 ms where a window move mounts pieces (here a 172 ms frame was gone).",
"evidence": "40 pieces, front ±10 mounted: drag p95 20.9 ms, flick 18.1 ms, step 18.5 ms, the same as with 14 (commits 8861494 and 70a7d58).",
"fix": "the window moves when the rail settles, a render at rest; mid-move it moves only if the front comes within four pieces of its edge.",
"format": 2,
"happened": "with 40 pieces, the window moved whenever the front passed three pieces from its centre, and each move mounted new pieces (fifteen animated styles and three pictures each) in the middle of a flick: a 172 ms frame.",
"kind": "my-mistake",
"learnedBy": "ai",
"lesson": "L-A651",
"packages": "react-native-reanimated@4.5.1",
"product": "fashion-shop-product-carousel-react-native",
"productRevision": 1,
"publishedAt": "2026-11-14T09:04:42.943Z",
"rule": "If a windowed list of animated items drops a frame mid-flick, move the mount window in a render at rest, and mid-move only when the front comes within a few items of the window's edge.",
"site": "https://upfork.dev",
"snippet": "```ts\n// before: the window follows the front every three items, mid-move too\nuseAnimatedReaction(() => Math.round(p.value), (now) => {\n if (Math.abs(now - centerAt.value) >= 3) { centerAt.value = now; scheduleOnRN(setCenter, now); }\n});\n// after: at rest it moves with the settled index; mid-move only near the edge\nuseEffect(() => { centerAt.value = index; setCenter(index); }, [index]);\nuseAnimatedReaction(() => Math.round(p.value), (now) => {\n if (Math.abs(now - centerAt.value) > reach - 4) { centerAt.value = now; scheduleOnRN(setCenter, now); }\n});\n```",
"title": "A mount window that moves mid-move mounts items mid-flick: move it when the motion settles, mid-move only near its edge",
"type": "lesson-version",
"url": "https://upfork.dev/lessons/L-A651",
"version": 1,
"why": ""
}